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2,370 results on '"Als-Nielsen, J"'

1. Atomic-Scale Visualization of Inertial Dynamics

Author

Lindenberg, A. M., Larsson, J., Sokolowski-Tinten, K., Gaffney, K. J., Blome, C., Synnergren, O., Sheppard, J., Caleman, C., MacPhee, A. G., Weinstein, D., Lowney, D. P., Allison, T. K., Matthews, T., Falcone, R. W., Cavalieri, A. L., Fritz, D. M., Lee, S. H., Bucksbaum, P. H., Reis, D. A., Rudati, J., Fuoss, P. H., Kao, C. C., Siddons, D. P., Pahl, R., Als-Nielsen, J., Duesterer, S., Ischebeck, R., Schlarb, H., Schulte-Schrepping, H., Schneider, J., von der Linde, D., Hignette, O., Sette, F., Chapman, H. N., Lee, R. W., Hansen, T. N., Techert, S., Wark, J. S., Bergh, M., Huldt, G., van der Spoel, D., Timneanu, N., Hajdu, J., Akre, R. A., Bong, E., Krejcik, P., Arthur, J., Brennan, S., Luening, K., and Hastings, J. B.

Published
2005

3. Critical behavior of the order-disorder phase transition in ß-brass investigated by x-ray scattering.

Author

Madsen, A., Als-Nielsen, J., Hallmann, J., Roth, T., and Lu, W.

Subjects
*PHASE transitions, *X-ray scattering, *SCALING hypothesis (Statistical physics)
Abstract

ß-brass exhibits an archetypical example of an order-disorder transition with a critical behavior that was previously investigated by neutron scattering. The data were well described by the three-dimensional (3d) Ising model but the relatively crude experimental resolution prevented an in-depth examination of the single-length scaling hypothesis, a cornerstone in the theory of critical phenomena. With the development of synchrotron x-ray experiments, high-resolution data could be recorded and surprisingly it was found that the single-length scaling did not hold in most critical systems, possibly due to strain originating from surface defects and/or impurities. In this paper we demonstrate single-length critical behavior using high-resolution x-ray scattering in ß-brass. The investigations confirm that ß-brass behaves like a 3d Ising system over a wide range of length scales comprising correlated clusters of millions of atoms. To vary the surface sensitivity, experiments have been performed both in Bragg reflection and Laue transmission geometries but without any substantial differences observed in the scaling and critical behavior. [ABSTRACT FROM AUTHOR]

Published
2016
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13. X-ray synchrotron study of packing and protrusions of polymer-lipid monolayers at the air-water interface

Author

Majewski, J., Kuhl, T.L., Kjaer, K., Gerstenberg, M.C., Als-Nielsen, J., Israelachvili, J.N., and Smith, G.S.

Subjects
Polymers -- Research, Lipids -- Analysis, Membranes (Biology) -- Research, Chemistry
Abstract

Lipids with bulky hydrophilic polymer headgroups were observed to have large fluctuations normal to the monolayer plane, causing a systematic roughening of the interface and a decline in the coherently Bragg-scattering tail thickness with increasing polymer-lipid content. Findings indicated that bulky hydrophilic moieties result into substantial out-of-plan protrusions of phospholipid monolayers and presumably bilayers, vesicles and biological membranes.

Published
1998

14. Design of two-dimensional crystals as models for probing the structure of the solid-liquid interface

Author

Gidalevitz, D., Weissbuch, I., Kjaer, K., Als-Nielsen, J., and Leiserowtiz, L.

Subjects
Cadmium -- Research, Alanine -- Research, Chemistry
Abstract

The effect of CdCl2 on the structure of mixed monolayer of steric acid and octadecylamine elucidated morphological changes of beta-alanine when grown in the presence of Cl- and Cl2+ ions. Cl2+ and Cl- ions, which bind to the sites, simulate mosaic crystalline pattern formation. This monolayer system exhibits ordered counterions of opposite charges.

Published
1994

20. Formation of secondary electron cascades in single-crystalline plasma-deposited diamond upon exposure to femtosecond x-ray pulses.

Author

Gabrysch, M., Marklund, E., Hajdu, J., Twitchen, D. J., Rudati, J., Lindenberg, A. M., Caleman, C., Falcone, R. W., Tschentscher, T., Moffat, K., Bucksbaum, P. H., Als-Nielsen, J., Nelson, A. J., Siddons, D. P., Emma, P. J., Krejcik, P., Schlarb, H., Arthur, J., Brennan, S., and Hastings, J.

Subjects
ELECTRONS, CHEMICAL vapor deposition, ULTRASHORT laser pulses, DIAMONDS, CRYSTALS, PHYSICS
Abstract

Secondary electron cascades were measured in high purity single-crystalline chemical vapor deposition (CVD) diamond, following exposure to ultrashort hard x-ray pulses (140 fs full width at half maximum, 8.9 keV energy) from the Sub-Picosecond Pulse Source at the Stanford Linear Accelerator Center. We report measurements of the pair creation energy and of drift mobility of carriers in two CVD diamond crystals. This was done for the first time using femtosecond x-ray excitation. Values for the average pair creation energy were found to be 12.17±0.57 and 11.81±0.59 eV for the two crystals, respectively. These values are in good agreement with recent theoretical predictions. The average drift mobility of carriers, obtained by the best fit to device simulations, was μh=2750 cm2/V s for holes and was μe=2760 cm2/V s for electrons. These mobility values represent lower bounds for charge mobilities due to possible polarization of the samples. The results demonstrate outstanding electric properties and the enormous potential of diamond in ultrafast x-ray detectors. [ABSTRACT FROM AUTHOR]

Published
2008
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24. Malaria Pigment Crystals: The Achilles' Heel of the Malaria Parasite.

Author

Kapishnikov S, Hempelmann E, Elbaum M, Als-Nielsen J, and Leiserowitz L

Subjects
Crystallography, X-Ray, Models, Molecular, Hemeproteins chemistry, Malaria parasitology, Plasmodium falciparum chemistry
Abstract

The biogenic formation of hemozoin crystals, a crucial process in heme detoxification by the malaria parasite, is reviewed as an antimalarial drug target. We first focus on the in-vivo formation of hemozoin. A model is presented, based on native-contrast 3D imaging obtained by X-ray and electron microscopy, that hemozoin nucleates at the inner membrane leaflet of the parasitic digestive vacuole, and grows in the adjacent aqueous medium. Having observed quantities of hemoglobin and hemozoin in the digestive vacuole, we present a model that heme liberation from hemoglobin and hemozoin formation is an assembly-line process. The crystallization is preceded by reaction between heme monomers yielding hematin dimers involving fewer types of isomers than in synthetic hemozoin; this is indicative of protein-induced dimerization. Models of antimalarial drugs binding onto hemozoin surfaces are reviewed. This is followed by a description of bromoquine, a chloroquine drug analogue, capping a significant fraction of hemozoin surfaces within the digestive vacuole and accumulation of the drug, presumably a bromoquine-hematin complex, at the vacuole's membrane., (© 2021 The Authors. ChemMedChem published by Wiley-VCH GmbH.)

Published
2021
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27. Macroscopic alignment of graphene stacks by Langmuir-Blodgett deposition of amphiphilic hexabenzocoronenes

Author

Laursen, B.W., Nørgaard, K., Reitzel, N., Simonsen, J. B., Nielsen, C. B., Als-Nielsen, J., Bjørnholm, T., Sølling, Theis Ivan, Nielsen, Martin Meedom, Bunk, Oliver, Kjær, Kristian, Tchebotareva, N., Watson, M.D., Mullen, K., Piris, J., Laursen, B.W., Nørgaard, K., Reitzel, N., Simonsen, J. B., Nielsen, C. B., Als-Nielsen, J., Bjørnholm, T., Sølling, Theis Ivan, Nielsen, Martin Meedom, Bunk, Oliver, Kjær, Kristian, Tchebotareva, N., Watson, M.D., Mullen, K., and Piris, J.

Abstract

e present structural studies of Langmuir V and Langmuir-Blodgett (LB) films of new amphiphilic hexa-peri-hexabenzocoronene (HBC) discotics, carrying five branched alkyl side chains and one polar group. The polar group is either a carboxylic acid moiety or an electron acceptor moiety (anthraquinone). Grazing-incidence X-ray diffraction (GIXD) and X-ray reflectivity, both utilizing synchrotron radiation, show that these amphiphilic HBCs form well-defined Langmuir monolayers at the air-water interface, with pi-stacked columnar structure where the HBC cores are rotated around the surface normal and tilted relative to the water surface. The intercolumnar distance is 20 A. The HBCs are confined to a layer lying on top of the layer of polar groups that are in contact with the water subphase. Efficient transfer of the monolayer of the anthraquinone-substituted HBC derivative to hydrophobic quartz substrates by vertical dipping gave well-defined multilayer Y-type LB films. Polarized optical spectroscopy, GIXD, and X-ray reflectivity measurements show that the LB films consist of at least two phases. Heating the films results in an irreversible rearrangement to a single macroscopically aligned phase of hexagonally packed columns oriented along the dipping direction with disk planes perpendicular to the columnar axes and stacked in a cofacial manner. This phase transition is analogous to the reversible transition observed in the bulk material.

Published
2004

30. Mode of action of quinoline antimalarial drugs in red blood cells infected by Plasmodium falciparum revealed in vivo.

Author

Kapishnikov S, Staalsø T, Yang Y, Lee J, Pérez-Berná AJ, Pereiro E, Yang Y, Werner S, Guttmann P, Leiserowitz L, and Als-Nielsen J

Subjects
Crystallization, Erythrocytes chemistry, Erythrocytes metabolism, Heme chemistry, Heme metabolism, Hemeproteins chemistry, Hemeproteins metabolism, Humans, Malaria, Falciparum drug therapy, Malaria, Falciparum metabolism, Plasmodium falciparum physiology, Antimalarials pharmacology, Erythrocytes parasitology, Malaria, Falciparum parasitology, Plasmodium falciparum drug effects, Quinolines pharmacology
Abstract

The most widely used antimalarial drugs belong to the quinoline family. Their mode of action has not been characterized at the molecular level in vivo. We report the in vivo mode of action of a bromo analog of the drug chloroquine in rapidly frozen Plasmodium falciparum -infected red blood cells. The Plasmodium parasite digests hemoglobin, liberating the heme as a byproduct, toxic to the parasite. It is detoxified by crystallization into inert hemozoin within the parasitic digestive vacuole. By mapping such infected red blood cells with nondestructive X-ray microscopy, we observe that bromoquine caps hemozoin crystals. The measured crystal surface coverage is sufficient to inhibit further hemozoin crystal growth, thereby sabotaging heme detoxification. Moreover, we find that bromoquine accumulates in the digestive vacuole, reaching submillimolar concentration, 1,000-fold more than that of the drug in the culture medium. Such a dramatic increase in bromoquine concentration enhances the drug's efficiency in depriving heme from docking onto the hemozoin crystal surface. Based on direct observation of bromoquine distribution in the digestive vacuole and at its membrane surface, we deduce that the excess bromoquine forms a complex with the remaining heme deprived from crystallization. This complex is driven toward the digestive vacuole membrane, increasing the chances of membrane puncture and spillage of heme into the interior of the parasite., Competing Interests: The authors declare no competing interest., (Copyright © 2019 the Author(s). Published by PNAS.)

Published
2019
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31. The phases of phosphatidyl ethanolamine monolayers

Author

Zabel, H., Robinson, I.K., Helm, C.A., Tippmann-Krayer, P., Kenn, R.M., Möhwald, H., Als-Nielsen, J., Kjær, K., Zabel, H., Robinson, I.K., Helm, C.A., Tippmann-Krayer, P., Kenn, R.M., Möhwald, H., Als-Nielsen, J., and Kjær, K.

Published
1992

34. Two-dimensional crystallography of amphiphilic molecules at the air-water interface

Author

Jacquemain, D., Grayer Wolf, S., Leveiller, F., Deutsch, M., Kjær, K., Als-Nielsen, J., Lahav, M., Leiserowitz, L., Jacquemain, D., Grayer Wolf, S., Leveiller, F., Deutsch, M., Kjær, K., Als-Nielsen, J., Lahav, M., and Leiserowitz, L.

Abstract

The advent of well-collimated, high-intensity synchrotron X-ray sources and the consequent development of surface-specific X-ray diffraction and fluorescence techniques have recently revolutionized the study of Langmuir monolayers at the air-liquid interface. These methods allowed for the first time the determination of the in-plane and vertical structure of such monolayers with a resolution approaching the atomic level. We briefly describe these methods, including grazing incidence X-ray diffraction, specular reflectivity, Bragg rods, standing waves, and surface fluorescence techniques, and review recent results obtained from them for Langmuir films. The methods have been successfully applied in the elucidation of the structure of crystalline aggregates of amphiphilic molecules such as alcohols, carboxylic acids and their salts, alpha-amino acids, and phospholipids at the water surface. In addition, it became possible to monitor by diffraction the growth and dissolution of the crystalline self-aggregates as well as structural changes occurring by phase transitions. Furthermore, the surface X-ray methods shed new light on the structure of the underlying ionic layer of attached solvent or solute species. Examples are given where singly or doubly charged ions bound to the two-dimensional (2D) crystal form either an ordered or diffuse counterionic layer. Finally, the surface diffraction methods provide data on transfer of structural information from 2D clusters to 3D single crystals, which had been successfully accomplished by epitaxial-like crystallization both in organic and inorganic crystals.

Published
1992

35. X-ray scattering studies of organic monolayers on electrolytic solutions: Arachidic acid on CdCl2

Author

Zabel, H., Robinson, I.K., Kjær, K., Als-Nielsen, J., Kenn, R.M., Böhm, C., Tippmann-Krayer, P., Helm, C.A., Möhwald, H., Leveiller, F., Jacquemain, D., Lahav, M., Leiserowitz, L., Deutsch, M., Zabel, H., Robinson, I.K., Kjær, K., Als-Nielsen, J., Kenn, R.M., Böhm, C., Tippmann-Krayer, P., Helm, C.A., Möhwald, H., Leveiller, F., Jacquemain, D., Lahav, M., Leiserowitz, L., and Deutsch, M.

Published
1992

39. Observation of Structural Anisotropy and the Onset of Liquidlike Motion During the Nonthermal Melting of InSb. Physical Review Letter

Author

Gaffney, K., Lindenberg, A., Larsson, J., Sokolowski-Tinten, K., Blome, C., Synnergren, O., Sheppard, J., Caleman, C., MacPhee, A., Weinstein, D., Lowney, D., Allison, T., Matthews, T., Falcone, R., Cavalieri, A., Fritz, D., Lee, S., Bucksbaum, P., Reis, D., Rudati, J., Macrander, A., Fuoss, P., Kao, C., Siddons, D., Pahl, R., Moffat, K., Als-Nielsen, J., Düsterer, S., Ischebeck, R., Schlarb, H., Schulte-Schrepping, H., Schneider, J., von der Linde, D., Hignette, O., Sette, F., Chapman, H., Lee, R., Hansen, T., Wark, J., Bergh, M., Huldt, G., van der Spoel, D., Timneanu, N., Hajdu, J., Akre, R., Bong, E., Krejcik, P., Arthur, J., Brennan, S., Luening, K., and Hastings, J.

Subjects
ddc:550
Published
2005

40. Formation of secondary electron cascades in single-crystalline plasma-deposited diamond upon exposure to femtosecond x-ray pulses

Author

Gabrysch, Markus, Marklund, Erik, Hajdu, Janos, Twitchen, D. J., Rudati, J., Lindenberg, A. M., Caleman, Carl, Falcone, R. W., Tschentscher, T., Moffat, K., Bucksbaum, P. H., Als-Nielsen, J., Nelson, A. J., Siddons, D. P., Emma, P. J., Krejcik, P., Schlarb, H., Arthur, J., Brennan, S., Hastings, J., Isberg, Jan, Gabrysch, Markus, Marklund, Erik, Hajdu, Janos, Twitchen, D. J., Rudati, J., Lindenberg, A. M., Caleman, Carl, Falcone, R. W., Tschentscher, T., Moffat, K., Bucksbaum, P. H., Als-Nielsen, J., Nelson, A. J., Siddons, D. P., Emma, P. J., Krejcik, P., Schlarb, H., Arthur, J., Brennan, S., Hastings, J., and Isberg, Jan

Abstract

Secondary electron cascades were measured in high purity single-crystalline chemical vapor deposition (CVD) diamond, following exposure to ultrashort hard x-ray pulses (140 fs full width at half maximum, 8.9 keV energy) from the Sub-Picosecond Pulse Source at the Stanford Linear Accelerator Center. We report measurements of the pair creation energy and of drift mobility of carriers in two CVD diamond crystals. This was done for the first time using femtosecond x-ray excitation. Values for the average pair creation energy were found to be 12.17 +/- 0.57 and 11.81 +/- 0.59 eV for the two crystals, respectively. These values are in good agreement with recent theoretical predictions. The average drift mobility of carriers, obtained by the best fit to device simulations, was mu(h)= 2750 cm(2)/V s for holes and was mu(e)= 2760 cm(2) / V s for electrons. These mobility values represent lower bounds for charge mobilities due to possible polarization of the samples. The results demonstrate outstanding electric properties and the enormous potential of diamond in ultrafast x-ray detectors.

Published
2008
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41. Self-aggregation of a,co-Alkanediols into Two and Three Dimensional Crystallites at the Air-Water Interface. Relevance to Ice Nucleation

Author

Popovitz-Biro, R., Ron Edgar, Majewski, J., Cohen, S., Margulis, L., Kjaer, K., Als-Nielsen, J., Leiserowitz, L., and Lahav, M.

Abstract

A correlation is presented between the crystalline structure of monolayers and multilayers of a,co-alkanediols HO-(CH2)„-OH (n = 16, 18, 19, 21, 22, 23, 24, 30) at the air-water interface and their function as ice nucleators. Structural elucidation was carried out by the following methods; grazing incidence X-ray diffraction, scanning force microscopy, cryo-transmission electron microscopy and external reflection Fourier transform-infrared spectroscopy.

Published
1996

42. Observation of structural anisotropy and the onset of liquidlike motion during the nonthermal melting of InSb.

Author

Gaffney, K J, Lindenberg, A M, Larsson, J, Sokolowski-Tinten, K, Blome, C, Synnergren, O, Sheppard, J, Caleman, C, MacPhee, A G, Weinstein, D, Lowney, D P, Allison, T, Matthews, T, Falcone, R W, Cavalieri, A L, Fritz, D M, Lee, S H, Bucksbaum, P H, Reis, D A, Rudati, J, Macrander, A T, Fuoss, P H, Kao, C C, Siddons, D P, Pahl, R, Moffat, K, Als-Nielsen, J, Duesterer, S, Ischebeck, R, Schlarb, H, Schulte-Schrepping, H, Schneider, J, von der Linde, D, Hignette, O, Sette, F, Chapman, H N, Lee, R W, Hansen, T N, Wark, J S, Bergh, M, Huldt, G, van der Spoel, D, Timneanu, N, Hajdu, J, Akre, R A, Bong, E, Krejcik, P, Arthur, J, Brennan, S, Luening, K, Hastings, J B, Gaffney, K J, Lindenberg, A M, Larsson, J, Sokolowski-Tinten, K, Blome, C, Synnergren, O, Sheppard, J, Caleman, C, MacPhee, A G, Weinstein, D, Lowney, D P, Allison, T, Matthews, T, Falcone, R W, Cavalieri, A L, Fritz, D M, Lee, S H, Bucksbaum, P H, Reis, D A, Rudati, J, Macrander, A T, Fuoss, P H, Kao, C C, Siddons, D P, Pahl, R, Moffat, K, Als-Nielsen, J, Duesterer, S, Ischebeck, R, Schlarb, H, Schulte-Schrepping, H, Schneider, J, von der Linde, D, Hignette, O, Sette, F, Chapman, H N, Lee, R W, Hansen, T N, Wark, J S, Bergh, M, Huldt, G, van der Spoel, D, Timneanu, N, Hajdu, J, Akre, R A, Bong, E, Krejcik, P, Arthur, J, Brennan, S, Luening, K, and Hastings, J B

Published
2005

43. Clocking femtosecond X rays.

Author

Cavalieri, A L, Fritz, D M, Lee, S H, Bucksbaum, P H, Reis, D A, Rudati, J, Mills, D M, Fuoss, P H, Stephenson, G B, Kao, C C, Siddons, D P, Lowney, D P, Macphee, A G, Weinstein, D, Falcone, R W, Pahl, R, Als-Nielsen, J, Blome, C, Düsterer, S, Ischebeck, R, Schlarb, H, Schulte-Schrepping, H, Tschentscher, Th, Schneider, J, Hignette, O, Sette, F, Sokolowski-Tinten, K, Chapman, H N, Lee, R W, Hansen, T N, Synnergren, O, Larsson, J, Techert, S, Sheppard, J, Wark, J S, Bergh, M, Caleman, C, Huldt, G, van der Spoel, D, Timneanu, N, Hajdu, J, Akre, R A, Bong, E, Emma, P, Krejcik, P, Arthur, J, Brennan, S, Gaffney, K J, Lindenberg, A M, Luening, K, Hastings, J B, Cavalieri, A L, Fritz, D M, Lee, S H, Bucksbaum, P H, Reis, D A, Rudati, J, Mills, D M, Fuoss, P H, Stephenson, G B, Kao, C C, Siddons, D P, Lowney, D P, Macphee, A G, Weinstein, D, Falcone, R W, Pahl, R, Als-Nielsen, J, Blome, C, Düsterer, S, Ischebeck, R, Schlarb, H, Schulte-Schrepping, H, Tschentscher, Th, Schneider, J, Hignette, O, Sette, F, Sokolowski-Tinten, K, Chapman, H N, Lee, R W, Hansen, T N, Synnergren, O, Larsson, J, Techert, S, Sheppard, J, Wark, J S, Bergh, M, Caleman, C, Huldt, G, van der Spoel, D, Timneanu, N, Hajdu, J, Akre, R A, Bong, E, Emma, P, Krejcik, P, Arthur, J, Brennan, S, Gaffney, K J, Lindenberg, A M, Luening, K, and Hastings, J B

Abstract

Linear-accelerator-based sources will revolutionize ultrafast x-ray science due to their unprecedented brightness and short pulse duration. However, time-resolved studies at the resolution of the x-ray pulse duration are hampered by the inability to precisely synchronize an external laser to the accelerator. At the Sub-Picosecond Pulse Source at the Stanford Linear-Accelerator Center we solved this problem by measuring the arrival time of each high energy electron bunch with electro-optic sampling. This measurement indirectly determined the arrival time of each x-ray pulse relative to an external pump laser pulse with a time resolution of better than 60 fs rms.

Published
2005

44. Atomic-scale visualization of inertial dynamics.

Author

Lindenberg, A M, Larsson, J, Sokolowski-Tinten, K, Gaffney, K J, Blome, C, Synnergren, O, Sheppard, J, Caleman, C, Macphee, A G, Weinstein, D, Lowney, D P, Allison, T K, Matthews, T, Falcone, R W, Cavalieri, A L, Fritz, D M, Lee, S H, Bucksbaum, P H, Reis, D A, Rudati, J, Fuoss, P H, Kao, C C, Siddons, D P, Pahl, R, Als-Nielsen, J, Duesterer, S, Ischebeck, R, Schlarb, H, Schulte-Schrepping, H, Tschentscher, Th, Schneider, J, von der Linde, D, Hignette, O, Sette, F, Chapman, H N, Lee, R W, Hansen, T N, Techert, S, Wark, J S, Bergh, M, Huldt, G, van der Spoel, D, Timneanu, N, Hajdu, J, Akre, R A, Bong, E, Krejcik, P, Arthur, J, Brennan, S, Luening, K, Hastings, J B, Lindenberg, A M, Larsson, J, Sokolowski-Tinten, K, Gaffney, K J, Blome, C, Synnergren, O, Sheppard, J, Caleman, C, Macphee, A G, Weinstein, D, Lowney, D P, Allison, T K, Matthews, T, Falcone, R W, Cavalieri, A L, Fritz, D M, Lee, S H, Bucksbaum, P H, Reis, D A, Rudati, J, Fuoss, P H, Kao, C C, Siddons, D P, Pahl, R, Als-Nielsen, J, Duesterer, S, Ischebeck, R, Schlarb, H, Schulte-Schrepping, H, Tschentscher, Th, Schneider, J, von der Linde, D, Hignette, O, Sette, F, Chapman, H N, Lee, R W, Hansen, T N, Techert, S, Wark, J S, Bergh, M, Huldt, G, van der Spoel, D, Timneanu, N, Hajdu, J, Akre, R A, Bong, E, Krejcik, P, Arthur, J, Brennan, S, Luening, K, and Hastings, J B

Abstract

The motion of atoms on interatomic potential energy surfaces is fundamental to the dynamics of liquids and solids. An accelerator-based source of femtosecond x-ray pulses allowed us to follow directly atomic displacements on an optically modified energy landscape, leading eventually to the transition from crystalline solid to disordered liquid. We show that, to first order in time, the dynamics are inertial, and we place constraints on the shape and curvature of the transition-state potential energy surface. Our measurements point toward analogies between this nonequilibrium phase transition and the short-time dynamics intrinsic to equilibrium liquids.

Published
2005

45. Clocking femtosecond X-rays

Author

Cavalieri, A.L., Fritz, D.M., Lee, S.H., Bucksbaum, P.H., Reis, D.A., Mills, D.M., Pahl, R, Rudati, J, Fuoss, P.H., Stephenson, G.B., Lowney, D.P., MacPhee, A.G., Weinstein, D, Falcone, R.W., Als-Nielsen, J, Blome, C, Ischebeck, R, Schlarb, H, Tschenscher, Th, Schneider, J, Sokolowski-Tinten, K, Chapman, H.N., Lee, R.W., Hansen, Tue, Synnergren, Ola, Larsson, Jörgen, Teschert, S, Sheppard, J, Wark, J.S., Bergh, M, Caleman, C, Huldt, G, van der Spoel, D, Timneanu, N, Hajdu, J, Bong, E, Emma, P, Krejicik, P, Arthur, J, Brennan, S, Gaffney, K.J., Lindenberg, A.M., Hastings, J.B., Cavalieri, A.L., Fritz, D.M., Lee, S.H., Bucksbaum, P.H., Reis, D.A., Mills, D.M., Pahl, R, Rudati, J, Fuoss, P.H., Stephenson, G.B., Lowney, D.P., MacPhee, A.G., Weinstein, D, Falcone, R.W., Als-Nielsen, J, Blome, C, Ischebeck, R, Schlarb, H, Tschenscher, Th, Schneider, J, Sokolowski-Tinten, K, Chapman, H.N., Lee, R.W., Hansen, Tue, Synnergren, Ola, Larsson, Jörgen, Teschert, S, Sheppard, J, Wark, J.S., Bergh, M, Caleman, C, Huldt, G, van der Spoel, D, Timneanu, N, Hajdu, J, Bong, E, Emma, P, Krejicik, P, Arthur, J, Brennan, S, Gaffney, K.J., Lindenberg, A.M., and Hastings, J.B.

Abstract

Linear-accelerator-based sources will revolutionize ultrafast x-ray science due to their unprecedented brightness and short pulse duration. However, time-resolved studies at the resolution of the x-ray pulse duration are hampered by the inability to precisely synchronize an external laser to the accelerator. At the Sub-Picosecond Pulse Source at the Stanford Linear-Accelerator Center we solved this problem by measuring the arrival time of each high energy electron bunch with electro-optic sampling. This measurement indirectly determined the arrival time of each x-ray pulse relative to an external pump laser pulse with a time resolution of better than 60 fs rms.

Published
2005

46. Observation of structural anisotropy and the onset of liquidlike motion during the nonthermal melting of InSb

Author

Gaffney, KJ, Lindenberg, AM, Larsson, Jörgen, Sokolowski-Tinten, K, Blome, C, Synnergren, Ola, Sheppard, J, Caleman, C, MacPhee, AG, Weinstein, D, Lowney, DP, Allison, T, Matthews, T, Falcone, RW, Cavalieri, AL, Fritz, DM, Lee, SH, Bucksbaum, PH, Reis, DA, Rudati, J, Macrander, AT, Fuoss, PH, Kao, CC, Siddons, DP, Pahl, R, Moffat, K, Als-Nielsen, J, Duesterer, S, Ischebeck, R, Schlarb, H, Schulte-Schrepping, H, Schneider, J, von der Linde, D, Hignette, O, Sette, F, Chapman, HN, Lee, RW, Hansen, Tue, Wark, JS, Bergh, M, Huldt, G, van der Spoel, D, Timneanu, N, Hajdu, J, Akre, RA, Bong, E, Krejcik, P, Arthur, J, Brennan, S, Luening, K, Hastings, JB, Gaffney, KJ, Lindenberg, AM, Larsson, Jörgen, Sokolowski-Tinten, K, Blome, C, Synnergren, Ola, Sheppard, J, Caleman, C, MacPhee, AG, Weinstein, D, Lowney, DP, Allison, T, Matthews, T, Falcone, RW, Cavalieri, AL, Fritz, DM, Lee, SH, Bucksbaum, PH, Reis, DA, Rudati, J, Macrander, AT, Fuoss, PH, Kao, CC, Siddons, DP, Pahl, R, Moffat, K, Als-Nielsen, J, Duesterer, S, Ischebeck, R, Schlarb, H, Schulte-Schrepping, H, Schneider, J, von der Linde, D, Hignette, O, Sette, F, Chapman, HN, Lee, RW, Hansen, Tue, Wark, JS, Bergh, M, Huldt, G, van der Spoel, D, Timneanu, N, Hajdu, J, Akre, RA, Bong, E, Krejcik, P, Arthur, J, Brennan, S, Luening, K, and Hastings, JB

Abstract

The melting dynamics of laser excited InSb have been studied with femtosecond x-ray diffraction. These measurements observe the delayed onset of diffusive atomic motion, signaling the appearance of liquidlike dynamics. They also demonstrate that the root-mean-squared displacement in the [111] direction increases faster than in the [110] direction after the first 500 fs. This structural anisotropy indicates that the initially generated fluid differs significantly from the equilibrium liquid.

Published
2005

49. X-ray Experiments for Students at the SLS Optics Beamline

Author

Flechsig, U., primary, Als-Nielsen, J., additional, Jaggi, A., additional, Krempaský, J., additional, Oberta, P., additional, Spielmann, S., additional, van der Veen, J. F., additional, Garrett, R., additional, Gentle, I., additional, Nugent, K., additional, and Wilkins, S., additional

Published
2010
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50. Advanced methods in scanning x-ray microscopy

Author

Menzel, A., primary, Dierolf, M., additional, Kewish, C. M., additional, Thibault, P., additional, Jefimovs, K., additional, David, C., additional, Bech, M., additional, Jensen, T. H., additional, Feidenhans'l, R., additional, Heegaard, A.-M., additional, Hansen, R., additional, Berthing, T., additional, Martinez, K. L., additional, Als-Nielsen, J., additional, Kapishnikov, S., additional, Leiserowitz, L., additional, Pfeiffer, F., additional, and Bunk, O., additional

Published
2009
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